Chickens Go Back — Way Back — To Their Roots

Scientist genetically engineered birds with legs similar to their prehistoric counterparts

Using genetic engineering, scientists say they have created chicken embryos that have the legs of long-dead dinosaurs.

Chickens already had dinosaur legs. But these are just, you know, older dinosaur legs. More interesting dinosaur legs. Dinosaur legs the likes of which our planet hasn’t seen in ages. But as we now all know, chickens are dinosaurs.

In fact, birds in general are dinosaurs. It’s true that all of the species that we consider dinosaurs are long extinct, and plenty of lineages went extinct, too. But one branch of the dinosaur family — the one that managed to shrink the fastest — produced the oldest common ancestor of all living birds.

A recent study used chickens to better understand how earlier dinosaurs may have strutted around back in the day. The main difference is that dinosaurs had tails, so scientists stuck toilet-plunger-like appendages on some chicken butts to see how the animals would manage. (They kind of strutted like dinosaurs, shifting their weight forward with wide and heavy steps.)

Scientist stuck toilet plunger-like appendages on the back of birds to better understand how the dinosaurs locomoted. Photo: Creative Commons

But that doesn’t mean that a chicken with non-chicken-dinosaur legs isn’t impressive. This is, in fact, a brilliant feat of genetic engineering. The chickens-with-legs-from-dinosaurs-that-were-not-chickens were developed by scientists at the University of Chile and are described in a paper published this month in the journal Evolution.

Modern birds have leg bones that are a tad different from those we see in their ancient ancestors. In older dinosaurs, the fibula was long and tube-shaped, reaching all the way down to the ankle. In modern birds, this bone thins out and shortens relative to the other bones in the leg.

But during embryonic development, there’s a period when the fibula seems poised to grow dinolike — so the researchers, led by Joâo Botelho, inhibited a gene to keep the leg from maturing in typical chickenlike fashion.

“The experiments are focused on single traits to test specific hypotheses,” study author Alexander Vargas said in a statement. “Not only do we know a great deal about bird development, but also about the dinosaur-bird transition, which is well-documented by the fossil record. This leads naturally to hypotheses on the evolution of development, which can be explored in the lab.”

Not only do we know a great deal about bird development, but also about the dinosaur-bird transition, which is well-documented by the fossil record.”

-Joâo Botelho. University of Chile head researcher

The same team had previously manipulated chicken genes to create embryos without the perching toe that modern birds have developed, and a group at Yale had modified beak-related genes to produce the kind of reptilian snout we associate with “true” dinosaurs.

All of this is possible because of the underlying genetic similarities between birds and their dino ancestors. As scientists get better and better at using the gene editing tool CRISPR, making changes like these — silencing or activating a few genes to bring an animal closer to its ancestors — may become routine.

But let’s not count our dino-chickens before they’ve hatched: For now, none of the experiments have attempted to produce living animals from the tweaked embryos.